In internal combustion engines disposed in vehicles, there is one type of engine including a device that is operated by negative suction pressure. In addition, there is such a device of the type including a negative pressure tank for storing the negative suction pressure. Such a tank protects against instances where the negative suction pressure sufficient to operate the internal combustion engine may be impossible to ensure, dependent upon different states in which the engine is run.
One example of such a device is a suction system that imparts swirl to intake air, which is aspirated into a combustion chamber, and thereby provides improved combustibility, with consequential respective reductions in a fuel consumption rate and harmful exhaust components. In some of the suction systems, branch pipes of an intake manifold are connected to a cylinder head of the engine through a swirl valve assembly, and further a swirl valve is disposed in the swirl valve assembly.
One example of such a swirl valve assembly of the suction system is shown in FIG. 18. In FIG. 18, reference numeral 202 denotes a suction system for a multi-cylinder internal combustion engine (not shown); 204 a swirl valve assembly; 206 a main body; and, 208, 210 first and second intake passages. In the suction system 202, the swirl valve assembly 204 has the first and second intake passages 208, 210 provided in the main body 206. The first and second intake passages 208, 210 communicate with a single combustion chamber (not shown).
The swirl valve assembly 204 has swirl valves 212 disposed in one of the first and second intake passages 208, 210, i.e., the second intake passage 210 in FIG. 18. The swirl valves 212 are opened and closed by a swirl valve actuator (not shown). The swirl valve actuator is a negative pressure-operated apparatus (not shown).
There is a negative pressure tank 214 separated from the main body 206. The tank 214 includes a tank chamber 216, in which negative suction pressure is stored. The negative suction pressure is introduced into the swirl valve actuator from the tank 214. The main body 206 includes a negative pressure introduction passage 218 for introduction of the negative suction pressure from the other of the first and second intake passages 208, 210, i.e., the first intake passage 208 in FIG. 18.
The negative pressure introduction passage 218 and the tank chamber 216 communicate with one another through a communication pipe 220. A check valve 222 is disposed substantially midway along the communication pipe 220 for permitting the negative suction pressure to be introduced from the negative pressure introduction passage 218 into the tank chamber 216.
In the suction system 202, an actuator control valve (not shown) serves to control the negative suction pressure that is supplied to the swirl valve actuator form the negative pressure tank 214. Then, the swirl valves are opened and closed to impart swirl to intake air that enters the combustion chamber, thereby providing improved combustibility.
Several examples of such a suction system are disclosed in published Japanese Patent Application Laid-Open Nos. 64-11358, 8-30457, and 3-41056, as discussed below.
In the suction system as disclosed in Application No. 64-11358, there is provided a tank body having a space isolated by both an inner space of a collector on the upstream side of an intake manifold and a partition wall. A one-way valve is provided on the partition wall.
In the suction system as disclosed in Application No. 8-30457, a negative pressure tank is disposed on branch members that are serially arranged on the downstream side of an intake pipe. The negative pressure tank is common to cylinders. The negative pressure tank is connected to an intake passage through a communication passage. A control valve is provided in the communication passage.
In the suction system as disclosed in application No. 3-41056, a closed space between a surge tank, which surge tank forms an intake expansion chamber, and a member that forms an independent intake passage extending in a curved manner downwardly from the top of the surge tank. The intake expansion chamber and the closed space communicate with one another through a negative pressure passage. A check valve is disposed in the negative pressure passage.
In the suction system 202 of a conventional type as illustrated in FIG. 18, the swirl valves 212 are disposed in the swirl valve assembly 204. In addition, the separate negative pressure tank 214 reserves the negative suction pressure that is supplied to the swirl valve actuator for opening and closing the swirl valves 212. However, such a separate tank 214 brings about inconveniences of an increased number of components, heavier weight, and restrictions on layout.
As a consequence, there is a suction system of the type having the negative pressure tank integrally assembled on either the branch pipes of the intake manifold or the surge tank, as described in the above-cited references.
However, as is the case with the suction system 202 shown in FIG. 18, an inconvenience of complex layout arises when the branch pipes of the intake manifold are connected to a cylinder head through the swirl valve assembly 204. This is because pipes must be laid from the negative pressure tank disposed on either the branch pipes or the surge tank to the swirl valve actuator that opens and closes the swirl valves 212 in the swirl valve assembly 204.